This is Keene’s story about having a very rare allergy to snails which might have something to do with the very common allergy he also has to dust mites. Allergy to house dust mites is fairly well known but could there possibly be any connection between that and the slimy molluscs he also has to avoid?

Cross reactivity between snail allergy and dust mite allergy

Keene has had one anaphylactic reaction to snails, in Holland while on a business trip.

He described the evening…

“My face just blew up but I hadn’t even noticed at first. We’d been out for a meal and I ordered snails, which I didn’t even like. Even while eating them I was thinking, I know I don’t like them, why did I order this? They’re just tasteless really and quite rubbery, the creamy garlic sauce is the only thing that makes them pallatable. You know when you wish you’d ordered what everyone else had? I was thinking I’m never eating snails again.

“But it wasn’t until about an hour later in the hotel bar that I realised something was wrong. It didn’t feel that bad and I didn’t realise what was happening until I went to the toilet and saw my face in the mirror. I looked weird. My whole neck and face was just massive.

“I went up to my room and kept monitoring the swelling and it was getting worse quite fast. I didn’t know what to do and didn’t want to go down to reception looking like that so I called for a doctor who came up to my room.

“The doctor told me I was having an allergic reaction and administered an antihistamine injection in my backside! He said it didn’t really matter what caused it, just that I got the drugs quickly and they did stop the swelling getting worse but my face and neck were still very swollen. I was uncomfortable and struggled to sleep and didn’t attend the training course the following morning because I still wasn’t right and the swelling had just about gone down by the afternoon.

“I thought about what might have caused the reaction but it was pretty conclusive. The only unusual thing I’d eaten was snails and I remembered the last time I’d had them on a cycling holiday in France, waking up in the night with a huge head cold, loads of snot and completely bunged up. I don’t get a lot of colds so I always wondered what caused that. It subsided quickly that time, not like a cold which tends to hang around a bit longer.

It is often not until after a diagnosis of a serious allergy that we analyse our food history and piece together previous exposures to the allergen which caused ever worsening effects. Keeping a record of what you ate and when you ate it can really help if you don’t know what’s causing your allergic reactions.

How does Keene cope with both of his allergies?

“Avoiding snails is relatively easy as they are really only ever on the menu in french restaurants, but avoiding dust is impossible.

I used to always get really swollen eyes when I worked away in hotels and if I’m doing anything dusty it makes me sneeze. I do a lot of DIY at home so this is a regular occurence but I find dust masks help with the worst of the symptoms.

“I sneeze every day actually but it’s not something that bothers me too much. I’m generally OK in my own house which isn’t particular dust free if I’m honest; it’s just in hotels, at work and staying at friend’s houses that I often get itchy swollen eyes. Not much you can do about that but antihistamines help to reduce the discomfort. I get these reactions far less now though so maybe my dust allergy has got a little better as I’ve got older.”

Should you avoid all shellfish or fish if you have a snail allergy?

He also has an inherrent dislike for any fish. He doesn’t choose to eat fish but can eat white fish and other fish like mackeral and salmon, but left to choose he would just never eat any fish.

Is this his body telling him to beware of the fishy stuff? He is also unsure about whether he should eat prawns as these seen to be lumped into the ‘shellfish’ group, but like all allergies, some people can react to one thing and others to the whole spectrum or family.

Snail allergy and dust allergy research papers

And if you’re interested in finding out more there are some links to various research studies below. One interesting connection is the third paper, about a young girl who became allergic to snails during dust mite allergy immunotherapy treatment. Anyone having dust mite allergy immunotherapy should be aware of this and take care with the shellfish.

A knowledge of cross-reactions between different allergens can facilitate the diagnosis of allergy. IgE cross-reactivity has been identified between house dust mite and snails. While most patients have mild symptoms, asthma and/or anaphylaxis may occur with these and other cross-reacting foods. It may be worthwhile to include measurement of IgE to some edible invertebrate animals in asthmatics, e.g. in mite allergic asthmatic patients who eat snails.

This study reports a 12-year-old girl who developed an anaphylactic reaction following snail ingestion during house dust mite (HDM) immunotherapy treatment. Radioallergosorbent (RAST) inhibition showed cross-reactivity between the two allergens, leading to consideration of HDM as the sensitizing agent. Children undergoing HDM immunotherapy treatment should be aware of the potential risks of hypersensitivity reactions to invertebrate foods.

What is the connection between snails and dust mites? Are dust and snails somehow related? Why would two seemingly totally unrelated things affect people? Maybe snails are allergic to dust too?

Do you have a snail allergy? Do you eat other shell fish and fish? Or do steer clear of prawns and other shellfish?